As a technique to compress a dynamic range, a picture is separated to an illumination component and a reflection component (Hereafter, it is called “a contrast component”), and the illumination component is compressed. A method for compressing the dynamic range with high contrast is known.
When separating a picture into an illumination component and a reflection component, as shown in FIG. 1, a brightness blur (Hereafter, it is called “a halo”) often occurs at a boundary of an object in the picture. In order to reduce the halo, various methods are proposed at the present.
For example, in JP-A 2003-8935 (Kokai), an epsilon filter (non-linear filter) having a superior ability to preserve edges is used as the filter for separating the illumination component. By controlling a threshold for the epsilon filter, a boundary of the object is suitably extracted. As a result, occurrence of the halo is reduced.
However, in the method for processing signal by separating the picture into the illumination component and the contrast component, if the picture includes noise in addition to the halo, the noise is preserved with enhancement in the picture.
In order to reduce the noise, after subjecting a noise reduction processing to an input picture, the input picture is separated into the illumination component and the contrast component. However, in this case, a signal component is not sufficiently separated from a noise component in the input picture, and a contrast in the signal component is further reduced.